Opto-electronic oscillator and method of generating an electrical carrier signal

An optical bandpass filter comprising:

• an optical source configured to generate an optical carrier signal having a carrier wavelength;
• an optical phase modulator configured to apply a sinusoidal phase modulation having
• a preselected frequency to the optical carrier signal to thereby generate two first order sidebands, located on either side of the optical carrier signal respectively, the two first order sidebands having a π phase difference between them;
• an optical phase shifter comprising an optical resonator configured to apply a substantially π phase-shift at a preselected wavelength within an optical spectrum of one of the first order sidebands;
• a photodetector configured to perform optical heterodyne detection of the optical carrier signal with both:
• said one of the first order sidebands π phase-shifted by the optical resonator;
• and
• the other of the first order sidebands,
• to generate an electrical output signal having a frequency equal to an frequency difference between the carrier wavelength of the optical carrier signal and the preselected wavelength at which the optical resonator is configured to apply the substantially π phase-shift.

A method of generating an electrical carrier signal, the method comprising:

• receiving an optical carrier signal having a carrier wavelength;
• applying a sinusoidal phase modulation to the optical carrier signal to thereby generate two first order sidebands, located on either side of the optical carrier signal respectively, the two first order sidebands having a π phase difference between them;
• applying a substantially π phase-shift to one of the first order sidebands at a preselected wavelength within an optical spectrum of said first order sideband;
• performing optical heterodyne detection of the optical carrier signal with both:
• said one of the first order sidebands substantially π phase shifted;
• and
• the other of the first order sidebands,
• to generate an electrical carrier signal having a frequency equal to a frequency difference between the carrier wavelength of the optical carrier signal and the preselected wavelength at which the substantially π phase-shift is applied;
• and
• providing a part of the electrical carrier signal to drive the sinusoidal phase modulation.